Muscle Histology

________ -> satellite cell -> muscle cell -> __________

mesenchymal cell, muscle fiber

Sarcolemma

cell membrane

Sarcoplasm

cytoplasm, has contractile proteins

sarcoplasmic reticulum

smooth endoplasmic reticulum

anti- desmin antibodies

IHC marker, protein of intermediary filaments present in the cytoplasm of smooth and skeletal muscle, marker of myogenic differentiation

anti-actin antibodies

IHC marker, contractile protein present in all types of muscle cells

anti-myoglobin antibodies

IHC marker, protein in skeletal muscle

anti-caldesmon antibodies

IHC marker, protein present in the cytoplasm of smooth muscle cells

skeletal muscle is under control of

CNS

Visceral muscle

morphologically identical to skeletal, attached to the soft tissues/part of different organs

rabdomyocytes

striated muscle cells

muscle fibers → joined together by _____________ rich in blood vessels and nerves

connective tissue

epimysium

around the entire muscle o a dense connective tissue layer

perimysium

around bundles or fascicles o a denser connective tissue sheath with few adipose cells

endomysium

around the individual muscle fibers o a delicate layer of reticular fibers o → with an extensive capillary network

Red skeletal fibers

high content of myoglobin, a rich vascularization, for continuous activity

Intermediate skeletal fibers

a large amount of glycogen o for rapid, strong contractions

White skeletal fibers

less vascularized, less myoglobin o adapted for rapid, strong but short contractions

Skeletal muscle fibers derived from _____ that form _______

myoblasts, multinucleated cells

sarcolemma is surrounded by

satellite cells and external lamina

Satellite cells

for muscle maintenance, repair, and regeneration in the adult, activated by the loss of muscle fibers

Integrins

in sarcolemma, receptors for laminins, role in organization and attachment of the basal lamina to the muscle cell

distrophyn-glycoproteins complex

in sarcolemma, role in stabilizing the cell membrane and connecting of the contractile apparatus to the extracellular environment

myoglobin

in sarcoplasm → iron- and oxygen-binding protein

creatin + creatine phosphokinaze/ creatin kinase (CK, CPK)

catalyses the conversion of creatin into creatinin (its level being in correlation with muscle mass and reflecting the function of kidney)

cytoskeleton of sarcoplasm is represented by

intermediate filaments that contain desmin

Sarcoplasmic reticulum - function

controls sequestration and release of calcium ions in sarcoplasm

triads

connects sarcoplasmic reticulum with T-tubule system, coupling nerve stimulation (depolarization) for contraction

myofibril - role

muscle contraction

Cohnheim fields

myofibrils in cross section

myofibril is made of thick myofilaments - consist of __________ & thin myofilaments - made up of ______

myosin, actin

sarcomere

functional unit of myofibril, bw two 2 z lines

actin/thin filament made of

F-actin filament chains and G-actin, with a myosin-binding domain on its surface

Tropomyosin

covers the myosin-binding site on the actin molecule, o prevents the binding of the myosin head to the G-actin

3 proteins of troponin

- troponin I (TnI) - binds to actin
- troponin C (TnC) - binds Ca2+
- -troponin T (TnT) - binds to tropomyosin

myosin II - made of

two heavy polypeptide chains and two pairs of light polypeptide chains

globular head of myosin contains

actin-binding region, ATP-binding region, light chain-binding region

Enzymatic digestion → with ________ cleaves the myosin

tripsin

Enzymatic digestion -> with _______ cleaves the heavy meromyosin into two segments

papain

_________ meromyosin (LMM) →the tail; o the _______ meromyosin (HMM) →the globular heads, lever arms, and the light chains

light, heavy

a actinin

protein regulating contraction, of z line

titin

protein regulating contraction, of the cytoskeleton inside the sarcomere

nebulin

protein regulating contraction, of cytoskeleton

tropomodulin

protein regulating contraction, regulates the length of the actin filament

What protein regulating contraction forms the M line

myosin-binding protein C and myomesin

muscle contraction causes no change in the length of

thick and thin filaments

____ must be available for the reaction between actin and myosin

ca+2

rigor mortis

lack of ATP (muscular stiffening and rigidity)

What determines a muscle fiber/muscle to contract?

nerve impulse/action potential from a motor neuron

What monitors the state of contraction?

central nervous system through muscle spindle +myotendinous junction

muscle fibers controlled by the same motor neuron form a

motor unit

presynaptic buttons contain ______ and _________-_______ _______ filled with the neurotransmitter acetylcholine

mitochondria and membrane-bound vesicles

AChe (acetylcholinesterase)

enzyme that breaks down acetylcholin in the muscle after the stimulus ends

proprioceptors of neuromuscular spindles monitors

length and the changes in length of the muscles

golgi tendon organ

monitors the intensity of muscle contraction, in tendons, made of collagen fiber bundles

Smooth muscle is made of

smooth muscle cells (leyomyocytes) + connective tissue

unlike skeletal muscle fibers, smooth muscle fibers retain their _____ ______

mitotic ability

2 functions of smooth muscle

able to contract
to synthesize proteins

cells are linked to each other by gap junctions →permit _______ ________ of the smooth muscle

synchronous contraction

dense areas of sarcolemma of smooth muscle

on the inner side of the plasma membrane, between the caveolae o contain α-actinin and receptors for laminin that ensure the link with the extracellular matrix

caveole of sarcolemma of smooth muscle

uptake of Ca2+ from the sarcoplasm in the resting muscle fiber o transmitting depolarization signals to the underdeveloped sarcoplasmic reticulum

int filaments of smooth muscle - contain

desmin in visceral m, desmin+vimentin in vascular smooth muscles

Contractile apparatus of smooth muscle

network of thick myosin filaments + thin actin filaments but without forming myofibrils

What replaces troponin in smooth muscle

caldesmon and calponin

smooth muscle - Ca2+ ions bind to ____ and form a Ca2+ -calmodulin complex

calmodulin

in smooth muscle, Ca+2 ions initiate contraction ...

from outside cell

sympathetic innervation of smooth muscle by

noradrenaline

parasympathetic innervation of smooth muscle by

acetylcholine

synchronization of contraction of smooth muscle accomplished through

gap jxn

Muscles of body can be divided into

skeletal, smooth, and cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR)